Hardness penetrator



' c. KENT 2,436,435

HARDNESS PENETRATOR Feb. 24, 1948.

Filed Feb. 26, 1945- IN V EN TOR. CARLETON V. KENT v ATTORNEY PatentedFeb. 24, 1948 Carleton V. Kent, :East Moline;, :Ill.,,:3ssignog l.America-n- Machinis -and Metalsh-InenhlozmYorlt v 'N. Y., a corporationof'llelaware: Application February 26, I945, Serial-Wu; f5l9'g-85-T (CL.Z3e-85);

Jl-Glaim.

This invention relates tothe testing: of'tlre hardness of materials andmore particularlwto penetrators or indenters used in zthez machines 'bywhich the hardness-of a specimen is testech. Gemerally' a test loadi-ot'a given: magnitude i's:.used':iiio' forcesuch azpenetrator or indenter'against surface of the specimen whose hardness is tobe determined; Adimensiom of the resulting inrpression is: utilized" as an indication.of. theharctness of thespecimem Sometimes the depth of the: impressionmade by the penetrator" is measured, but more; commonly .arsurfacedimension of the. impression-is used as the-'basisfor the computati'onof the hardiness indexof" the specimens. known systems fortestinghardness are those; us ing a hardened steel ball referred to asa Brinellball; a e sided diamontrpyramid'whose Sidesare symmetrical with-each:other and intersecti'rr four cutting" edges having the same angle called'the Vickers"" pyramid and 'ai-sided pyramid in which two: oppositecutting: diagonal edges make a large angle with: each other While two:other cutting edges i n a plane perpendicular to that of the first-twomake asomewhatsmaller angle-with each other, known-as the Knoop pyramid.

Both types of" pyrami'ct =penetratorspermit greater accuracy in readingthe size ofthe: irn pression than :therBr'inell' ball. The Knoop pyramidparticularly has certainadvantages overthe;

other types of impression; specifically:

1. For the same area-ofimpression the length of thelonger diagonal ofthe impression created by-the Knoop: pyramid is greater than the lengthof the diagonalfin thevickers impression; There-- fore there will be arelatively smaller observational error in reading theKnoop-impression=..

2'; Withsome materials the 'material'displaced by-the indent'er causes arounded-ridge-around-the impression: which makes: it reot treading. Nosuch ridge is, formed' adjacent to the apexes of'the angles'forming theend's of the longer diagonal of impression;

3. In materials where the impression contracts after "the removal of thepenetr tor, no: tion takes place on the long" diagonal of the linepressionofia Knoop indent'eri;

It'isw-aniobject of the present invention to provide a penetrator "fortesting machine which retains the v aforementioned advantages the Knooppyramid but is easier and Cheaper-to produce than -the:pyramidal.penetrator; To make the-readihgs-oi: pyramidal. penetrators: conform: toanexistin'g; standarwitris:necessary that thefour Among the. best hard'to secure a-con the-penetrate: "which 'inventionwilllanpeareasmhe:hetWeer-r mush- .-.rpaiiar-cdfxpl'anes and all the planes :must: passthrough: assume-point". By contrast there is only a single curved-'outti'ng'edge, easily generated hy-existinagtmechanfcal equipment; inForms thesubject of this :the: line =oI-aqoplioatibn of the test load;In.one?torm ofitheinventiorr theindentin'g surxfiace or the-:penetraliorcomprises portions of'two 'slmfaces fiarming parts of two Scrmicalisimilar :coamial: cones;- the common axis of the -men to:be-testedt Suchcoaxial conical surfaces readily-- homeroom-d ny conventional methods ona tool grinder.

Itdsanother'dlfiect ofthe invention to provide tsapplied-tosaitrspecimeni further object ofthe invention "is to provideA- still further-object" of; the invention is to provideapenetratorhavirig .a. single curved cutting edge whicn isremov'a-bly, andpreferably *t'urnably'; mounted-leer on a; holder;

Another 'ohject'oflth'e' invention is. tov provide a penetrator ofharden'edimaterial which ismagnetically'supported'ln'.aholderof'adifi'erentcomposition.

Still: another. obiiect .of the. invention. is. to pror vrcle apenetrator:whichislpanticularly well-suit.- .edf.fornerforminghardnesstestsl on plastics.

Qthei: obiects features andladvantages oi the qescriptiomproceed's,reference being had to the accompanying; draw ings-imwlnch:

Fig h I fshowsa as front 'vievwof theinventiona.

Eighth lfiraz'siiierliiewdfi the penetratorshown-in ili igih sen-pramnewton-the impression "leftin the specimen by the penetrator shown in-Figs. 1 and 2 Thar-modified" fOr-In-ofpenetrat'or shown Figsz antl-leaves'the' same impression;

Fig:- l 'i's a front vi'ewaxinartly in section, ofaa modified'renetratoirzsmall portions of the conical surfaces "that permits thecomparison of readings Fig. is a side view of the modified form of thepenetrator shown in Fig. 4.

In Figs. 1 to 3 the numeral I denotes a speciimen whose hardness is tobe determined. 2 is a bar having its lower end ground so as to form twoconical surfaces 3 and I3, each of these conical surfaces being part ofa cone whose axis 4-5 extends perpendicularly'to th'axis "(i- 1 of thepenetrator. Since hardness impressions are normally made with thepenetrator at right angles to the surface of the specimen, ordinarily beparallel to men I. The two conical surfaces 3, l3 meet in an an: IBwhich forms the'singlecutting edge of the penetrator. any one of severalangles 9, depending upon the angle most suitable for indenting theparticular type of material. In Figure 1 this angle 9 is the surface ofCones 3, 13 may be formed with I the axis 4-5 will thespeci-.--

- projects.

shown as approximately 45 but it maybe se- I lected to suit the hardnessand characteristics of particular types of specimens tov be tested. Ingeneral, the softer the specimena'the larger will ,be the angle chosen.

As will be seen from the:drawing, the trator has two planes of symmetry,one being defined by the axes 45 and B---'! and. the other beingperpendicular thereto and containing axis 6-1. There is no cutting edgein the first-named .planeoi symmetry, the only cutting edge l5 beingsituated in said second plane perpendicular to the axis 4-5. Theshape-of the cutting edge i5 is that of an arc of a circle. Any sectiontaken through the active (conically ground) portion of the penetratorparallel to said last-named plane of symmetry is delimited by a circularcurve having its center on the axis 4-5.

The section taken through the other plane of symmetry, that ;.is, theplane containing axis 4-5 as well as axis I6-l is of V-shape with thesides of the V straight lines.

. If the penetrator shown inrFigs. land 2 is forced against the specimenI so that the cutting edge 15 penetrates the specimen as shown at 8, the

impression made will be of lenticular shape. The lenticular figure l2shownin Fig. 3, is bisected by the longitudinal line l9 created by' thecut- .ting edge (5 and the side walls I? and i8 of this impression arecurved surfaces corresponding to 3 and i3 of the penetrator. At each-ofthe two ends and [5 of the lenticular figure l2 the sides of "the latterand theline i!) join in, a single point which can be readily observed,such; as by amicroscope. The distance between the points M and it willbe used as index of the hardness of the particular specimen tested.

It has been found that thehardness readings obtained by the use of thedouble-cone penetratordescribed bear in .fixed relation to the readingssecured by other penetratorsystems. in par ticular .by. the systemsusing pyramidal penetrators; This permits the'use of a'conversion factoro i ed under this system with "those "obtained under other systems. Q l

The body on which the conical surfaces 3, l3 are formed may "consist ofhardened steel. In some cases it maybe advisable to tip the steel bar 2with a particularly hard material, such as -Carboloy, and to grind" theconical surfaces 3, {-3 thereon. i

In the modification shown in Figs. 4 and 5 the penetrator proper,generally indicated at 2! is again of double conicalshape. but insteadof being formed in one piece with the shaft has in -ous mannersdifferent from the -ed. In particular iprising, in combination.

' on both sides of the roller coaxially with the common axis of the twocones 3, l3. The holder 26 is fork-shaped having two downwardlyextending prongs 30, 32 in which the studs 22, 24 find their bearingsand which leave between themselves an opening 28, into which the roller29 With this arrangement the roller 20 may be rotated from time to timeto bring into play new indenting surfaces corresponding to a new sectionof the cutting edge l5, whereby the useful life of the penetrator may begreatly pr0 longed. 'T

It will be obvious that, if only a rotatable mounting of the {roller 20relative to the holder 26 is desired, this may be achieved also invarione shown in Figs. 4 and 5, such as by proviidng the roller 20 withone or more axial bores and have this roller supported by two studs orby a shaft formed integral with, or secured to, the holder 26 so thatthe wheel may turn on said studs or on said shaft.

The arrangement shown in Figs. 4 and 5, however, wherein the studs 22,24 form part of the roller 20 and the'holder 26 has two slots 34 whichare open at their lower end so that the studs may be slippedinto theseslots from below, is

very convenient'for the reason that it lends itself readily to holdingthe penetrator in place solely by magnetic means without the necessityof any mechanical retaining members. If the holder 26 34 and retainedtherein as soon as the studs 22, .24 of the roller-:20 are broughtreasonably close to and below the slots 34 in the holder 25; A furtheradvantage of this arrangement is that one penetrator can readily beexchanged for another having a different angle and the substitution ofthe one'penetrator for the other in the holder is only a matte'r ofseconds.

Roller 20 may be of hardened steel, its symmetrical form lending itselfreadily to hardening.

One of the advantages of this system is that it permits the selection ofthe proper size of roller and the proper cone angle that is best adaptedto the general-type of specimen that is to be testit has been found thata double-cone penetrjator of the proper size and angle gives betterresults in the testing of plastics than those systems of hardnesstesting that were primarily developed for use on metals.

, thefmaterial is distorted by the flat sides and numerous angles of theother indenters.

What I claim. is: A penetrator for adapted to make a hardness testingmachines lenticular impression, coma hardened piece whose cutting edgeis formed bythe intersection of two conical surfaces, means for loadingany part of said circular cutting edge, said means including hearings onthe axis of said cones and a shank Number having bearing surfaces sospaced as to transmit 1, 5

an axial load from the shaft axis to the speci- 5 2,254,162

men along a diameter of the circular cutting edge 2,335,235 which isnormal to the specimen.

CARLETON V. KENT. Number REFERENCES CITED 1 10 358,509

The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Name Date Ames Apr. 1, 1919 Wyman Aug. 26, 1941Clifton i. Nov. 30 1943 FOREIGN PATENTS Country Date Germany Sept. 11,1922

